Death by Coffee. Don't let it happen to you.

1 AM
August 15, 2007

Instant coffee should come with a health warning, and a special number to call in case you accidentally get some in your mouth. I found this out when I asked on Twitter, “is there enough caffeine in one jar of coffee to kill me?”. As is often the way with the lazyweb, my friends were only too eager to help:

Step-by-step to a southerly setting sun

The last paragraph of my previous post wasn’t particularly clear. Here’s a step-by-step guide to modelling the Sun’s direction at sunset, using only a ball, a lamp, and a texta.

Put a lamp up one end of the room. This will be the Sun.

Get a ball to represent the Earth. Anything between a tennis ball and a basketball will do.

On the Earth, select a spin axis (I used the inflation nipple as the North pole, but you can draw in the poles if you have to.)

Orient the ball so the spin axis is vertical. The top half of the Earth the northern hemisphere, and the bottom bit the southern hemisphere. Draw in the equator.

Tilt the spin axis of the Earth 23 degrees away from the sun to represent the southern hemisphere summer. The southern pole will now be a little closer to the Sun than the northern pole.

Draw in a line of longitude (i.e a line running from the North pole to the South pole), on the side of the ball closest to the light. On this line, it is noon. The point on the line closest to the light is on the Tropic of Capricorn. (digression: You may notice that the north pole is in shadow, and has no light at midday. If you draw in the line of longitude for midnight, you will find the parts of the southern hemisphere that have midnight sun.)

Pick a point about half way down the Southern Hemisphere and draw in the line of latitude for that point.

Around the side of the ball, where that line of latitude crosses from light into shadow, is a point where sunset (or sunrise) is taking place. If you stand behind the ball and sight back to the light across that point, you will see that, from the Earth’s inhabitant’s point of view, the Sun is south of the line of latitude.

If that doesn’t make sense, please drop me a line. I will come and explain it to you, complete with ball, texta, and lamp for the low, low price of one soft drink.

Sydneyside Southerly Sunset

If you are located further South than the Tropic of Capricorn, then the Sun will never be directly overhead, and furthermore will only appear in the Northern half of the sky.

I predicted that – this far South – the Sun would always set somewhat North of due West.

Makes sense to me. But then Julian’s father observed, in direct contraction to Julian’s well-constructed argument, that the Sun was setting to the south of west. Interesting.

I searched a bit and found PyEphem, a Python library for calculating the position of heavenly bodies. It is based on a C library and required a bit of huffing and puffing to get it to compile on Windows. I hacked the code just the teeniest bit to get rid compile errors, then ignored several pagefuls of warnings. But it seems to work.

This little script calculates where the Sun sets in late December, 2006, asssuming “this far South” means Sydneyairport, or thereabouts:

In other words, this script supports Julian’s father’s observation that the sun sets significantly to the south of west this time of year in Sydney. (Assuming, of course, that PyEphem is accurate, that my mangled compile of PyEphem didn’t affect anything serious, and that the above script is bug free.)

For a more concrete confirmation, I’d suggest using a ball as the Earth – rather than a fist – and then put on a lamp at the other end of of the room to represent the Sun. Tilt the ball back on its axis so that the noon day sun falls on the southern end of the ball. Now, look for sunrise and sunset down the side of the ball, and check the direction of the lamp, relative to east and west on the ball.

Google ate my feeds

3 AM
October 4, 2006

I was quite enjoying the new Google Reader for a while there. Then it started showing me items I’d already read. Then it started miscalculating the counts on the left hand side. Now it tells me that I am not subscribed to any feeds at all. It’s not normal for Google to just forget stuff is it?

Update: I was being a doofus. See below.

Actually, I think I have an explanation. I blame Simon. I reckon the sudden shift in Internet traffic patterns, caused by billions around the world wanting to check out the new item on Simon’s RSS feed, broke Google.

Update: Just figured it out. It’s quite interesting, in a way. It turns out I had two Google Accounts under different email addresses, and I was signed into Gmail with one account, and Google Reader with the other. I had just assumed they shared a login session, but obviously not. Just to be sure, I deleted the second account, and I am relieved – beyond my ability to express to any non-geek – to learn Google hadn’t lost my feed list.